Serial Communication (C# Windows Forms)

Question

Okay so I'm trying to do a two-way communication from C# to Arduino (using FTDI232) and viceversa, from Arduino to C#.
Here's the code:

   public partial class Form1 : Form  
       {  
           public SerialPort myPort;  
           private DateTime dateTime;  
           private string inData;  
           const string com = "COM8";  

           public Form1()  
           {  
               InitializeComponent();  
           }  
           private void start_btn_Click(object sender, EventArgs e) // TURN ON LED  
           {  
               myPort = new SerialPort();  
               myPort.BaudRate = 9600;  
               myPort.PortName = com;  
               try  
               {  
                   myPort.Open();  
                   myPort.WriteLine("A");  
                   myPort.Close();  
                   error_tb.Text = "";  
               }  
               catch (Exception exc)  
               {  
                   MessageBox.Show(exc.Message, "Errore");  
               }  
           }  
           private void stop_btn_Click(object sender, EventArgs e) // TURN OFF LED  
           {  
               myPort = new SerialPort();  
               myPort.BaudRate = 9600;  
               myPort.PortName = com;  
               try  
               {  
                   myPort.Open();  
                   myPort.WriteLine("B");  
                   myPort.Close();  
                   error_tb.Text = "";  
               }  
               catch (Exception exc2)  
               {  
                   MessageBox.Show(exc2.Message, "Error");  
               }  
           }  
           void MyPort_DataReceived(object sender, SerialDataReceivedEventArgs e)  
           {  
               inData = myPort.ReadLine();  
               this.Invoke(new EventHandler(displayData_event));  
           }  
           private void displayData_event(object sender, EventArgs e)  
           {  
               dateTime = DateTime.Now;  
               string time = dateTime.Hour + ":" + dateTime.Minute + ":" + dateTime.Second;  
               values_tb.Text = time + "\t\t\t\t\t" + inData;  
           }  
           private void Form1_Load(object sender, EventArgs e) // PRESS PHYSICAL BUTTON TO SEND DATA  
           {  
               myPort = new SerialPort();  
               myPort.BaudRate = 9600;  
               myPort.PortName = com;  
               myPort.Parity = Parity.None;  
               myPort.DataBits = 8;  
               myPort.StopBits = StopBits.One;  
               myPort.DataReceived += MyPort_DataReceived;  

               try  
               {  
                   myPort.Open();  
                   values_tb.Text = "";  
               }  
               catch (Exception exc3)  
               {  
                   MessageBox.Show(exc3.Message, "Error");  
               }  

           }  



           private void exit_btn_Click(object sender, EventArgs e) // Exit from Application  
           {  
               Application.Exit();  
           }  

           private void button2_Click(object sender, EventArgs e)   
           {  
               try  
               {  
                   myPort.Close();  
               }  
               catch (Exception exc4)  
               {  
                   MessageBox.Show(exc4.Message, "Error");  
               }  
           }  
       }  

1. I have three problems. One is when I want to close the application, I want the Serial Communication to turn off, because I made it automatically open using Form1_Load, as soon as you start the debug, it also opens Serial Communication, and it remains on, but I don't want to use a button that I have to click first to close the application. I need to close Serial Communication automatically after I close the application.
2. The second problem is with the Serial Port that denies the communication, what I mean is that I need to switch from Receiving Data to Sending Data. Here's a picture of what it looks like: Application Image
3. The the third problem is the LED one. Well its similar to the second one, but this time when I click the button OFF, I want it to switch back to Receiving Data. Here's the picture:
   Application Image 2
   • This code is only temporary. I needed it to turn off the Serial Communication private void button2_Click(object sender, EventArgs e)
     {
     try
     {
     myPort.Close();
     }
     catch (Exception exc4)
     {
     MessageBox.Show(exc4.Message, "Error");
     }
     }